Pollen Images of Selected British Flora: Part 3
Total Page：16
File Type：pdf, Size：1020Kb
Page 176 Family: Poaceae SEM images courtesy:SEM images Neville Rachel Phleum pratense Timothy Collection date: SEM date: 14/1/6 Location: Phleum pratense is a monoporate grain with the exine verrucate. Porus is circular, well defined and prominent . The nexine is thickened around the porus to form the costa. A native plant common to both agricultural land and waste places. Height: 1.5m. SEM images courtesy:SEM images Neville Rachel Poa trivialis Rough Meadow-grass Collection date: SEM date: 14/12/06 Location: Poa trivialis is a monoporate grain with the exine verrucate to micro-verrucate with a grater portion of micro-verrucae than verrucae. Porus is circular, well defined and prominent . The nexine is thickened around the porus to form the costa. A native plant common to open areas such as rough grassy places, wasteland and cultivated ground preferring moist situations. Height: 75cm. SEM Pollen images of selected British flora Page 177 Poaceae family summary. There have been many attempts to distinguish between pollen grains of members of the Poaceae ( formerly Graminaceae) family, attempts have been made by Beug (1961); Grohne (1957); Gourham (1969); Anderson (1979); all have met with limited success (Fageri and Iversen, 1989). The general consensus of these researchers was that the size of the pollen grains varied between that of cultivated cereals and wild grasses; the cereal crops produced large pollen grains on average but there was also variability in size amongst species also (Moore et al, 1991, p9 100). To determine size accurately and develop a solid analysis of pollen grains care needs to be taken that the pollen grains do not collapse as many did during this analysis. Moore et al (1991) cites Anderson and Iversen (1989) that success in determining pollen grain size was possible using silicone oil under light microscopes and that they were able to group many members of the Poaceae family into genus categories based on size. Other less intrusive methods of microscopic analysis such as confocal miscoprosy might alleviate the grain ‗collapse syndrome‘ and thus provide accurate sizes for individual grains hopefully further defining individual species. SEM Pollen images of selected British flora Page 178 Family: Polygalaceae Polygala calcarea Chalk Milkwort Collection date: 30/4/07 SEM date: 2/5/07 Location: Castle Hill, West Sussex Polygala calcarea pollen grains are polyzonocolporate, psillate and with a clear endopori centered around the equator but not exceeding one quarter the length of the grain. The apocolpia are designated with large somewhat irregular shaped depressions. The colpi are quite wide and obtuse-ended forming a equatorial girdle. The grains are flat to slightly depressed at the poles while retaining a rectangular appearance equatorially. A native plant found only on calcareous grassland. Height: 10cm. Polygalaceae family summary. Polygala calcarea pollen grains are polyzonocolporate, psillate and with a clear endopori centered around the equator but not exceeding one quarter the length of the grain. The pollen grain shape is oblong in equatorial view and elliptic-obtuse in polar views. The pollen grain shape and the arrangement of the colpi makes this an easily identifiable species, with only one plant similar in character but still easily identifiable from Polygala: Viola arvensis. Moore et al (1991, pp. 160) identifies Polygala to the species level only, although Stace (1997. pp. 467) identifies 7 other species, hybrids or subspecies. Further study is warranted to determine is there are distinct differences in the remainder of the genera found in the British Isles. SEM Pollen images of selected British flora Page 179 Family: Polygonaceae Polygonum maculosa Redshank (formerly: P. persicaria) Collection date: 28/607 SEM date: 29/6/07 Location: Clayton, West Sussex Polygonum persicaria is an orbicular polypantoporate, foveolate, eureticulate pollen grain. Each porus is small but filling the bottom of the lumina in the reticulum, thus the exine sculpturing is not interrupted by the pori. The lumina are not-porate but appear to have baculate to granulate floors. A native weed, occasional to field margins, waste ground and other marginal areas. Height: 75cm, but usually procumbent spreading more than its height. Rumex acetosella Sheep’s Sorrel Collection date: 19/5/07 SEM date: 25/5/07 Location: Ardingly Reservoir, West Sussex Rumex acetosella is a tetrapantocolpate grains with each ectocolpus with a more or less circular endoporus in the middle. Ectocolpi are longer often nearly or actually synocolpate. The pori are distinct. Pollen grains are small usually <28µm in size. Sculpture is sometimescontrasting with winding or sinuous duplicolumellate muri. A native plant comonly found on heaths, short grassland and wasteland; to about 1m in height. SEM Pollen images of selected British flora Page 180 Polygonaceae family summary. Polygonum persicaria is an orbicular polypantoporate, foveolate, eureticulate grain while Rumex acetosella is a tetrapantocolpate pollen grain. The two species are quite distinct both morphologically and floristically. P. maculosa has similar pollen morphological characteristics to G. molle. Moore et al (1991, pp. 162) does define the pollen morphological characteristics of R. obtusifolius, R. longifolius, R. palustris, R. aquaticus, and R. hydrolapathum and expects identification may be possible of R. aquaticus based on its grain dimensions but not sculptural details while Polygonum pollen grains according to Moore cannot be identified beyond the genus level. Stace (1997, pp. 184-196) lists 17 species, hybrids or subspecies of Polygonum and 69 species, hybrids, varieties and subspecies of Rumex, thus intonating the complexity of this family; the family also includes a further five genera; although with only a few species per genera. These numbers and familial relationships demonstrate the complexity of this family questioning the validity of pollen analysis beyond perhaps the species level for the hybrids, varieties and subspecies as it is anticipated that little differentiation would occur in pollen morphology beyond that phase. SEM Pollen images of selected British flora Page 181 Family: Primulaceae Anagallis arvensis Scarlet Pimpernel Collection date: 11/5/07 SEM date: 25/5/07 Location: Stamnar Woods, West Sussex Angelis arvensis pollen grains are < 36µm in size, elliptic-obtuse, trizonocolpate, eureticulate with the colpi almost running the full length of the grain and terminating in the pole. The colpi is narrow, slit like, sunken, with no differentiation at the equator or the poles. Exine is porate-rugulate with the lumina sizing decreasing towards the colpi. A native plant found on waste ground and arable land. Height: 35cm. Cyclamen coum Eastern Sowbread Collection date: 1/3/07 SEM date: 21/3/07 Location: Wakehurst Place, West Sussex Cyclamen coum pollen grains are elliptic-obtuse, trizonocolpate, psilate with the colpi almost running the full length of the grain and terminating in the pole. The colpi is narrow, slit like, sunken at the equator but also wider at this point. The colpi membrane is granulate, although finely so. Grain shape is quite distinct, circular to circular-oblong in equatorial view and circular in polar view. An introduced plant that may be seen along roadsides and as an escapee from the garden where it is still commonly cultured. Height: 25cm. SEM Pollen images of selected British flora Page 182 Family: Primulaceae Lysimachia nummularia Creeping Jenny Collection date: 19/5/07 SEM date: 25/5/07 Location: Ardingly Reservoir, West Sussex Lysimachia nummularia pollen grains are < 36µm in size rhombic-obtuse trizonocolpate, eureticulate with the colpi almost running the full length of the grain and terminating before the poles. The colpi is wide, opening towards the equator. The exine is porate-rugulate with the lumina sizing decreasing towards the colpi. This particular sample shows extensive pollen grain collapse. A native procumbent plant common to damp woods and other similar situations, often used in the garden as a groundcover from which it may escape and naturalize. Height: 5cm. Primula veris Cowslip Collection date: 10/4/07 SEM date: 18/4/07 Location: Wakehurst Place, West Sussex Primula veris pollen grains are rhombic-orbicular polyzonocolpate grains with flattened poles but slightly wider at the equator in equatorial view. The sculpture is eureticulate to suprareticulate and consistently scattered across the exine with small lumina and possible perforations in the floor of these. The mesocolpia is slightly convex with a wide colpi sunken and sinuous and terminating obtusely before the poles. P. veris is a native plant commonly occurring on grassland that has rich calcareous soils. Height: 30cm. SEM Pollen images of selected British flora Page 183 Family: Primulaceae Primula vulgaris Primrose (pin eyed) Collection date: 10/4/07 SEM date: 18/4/07 Location: Wakehurst Place, West Sussex Primula vulgaris pollen grains (pin eyed) are rhombic-orbicular polyzonocolpate grains with flattened poles. The sculpture is eureticulate to suprareticulate and consistently scattered across the exine with small lumina and possible perforations in the floor of these. The mesocolpia is slightly convex with a wide colpi sunken and sinuous and terminating obtusely before the poles. A number of the grains show extensive collapse. A native of woods, damp meadows and hedges. Height: 35cm. Primula vulgaris Primrose (thrum eyed) Collection date: 10/4/07 SEM date: 18/4/07